Systems, methods, and devices for isolating portions of a wellhead from fluid pressure

ABSTRACT

A wellhead system is provided. In one embodiment, the wellhead system includes a bypass sleeve for temporarily isolating portions of a wellhead assembly from pressurized fracing fluid. The bypass sleeve may include a generally tubular body having a tool interface, a lock ring disposed at least partially around the body, and an anti-rotation device coupled to the body. In some embodiments, the anti-rotation device includes a resilient member disposed in a cavity in the body, and an anti-rotation member biased away from the body by the resilient member. The anti-rotation member of some embodiments extends radially outward from the body.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. Non-Provisionalpatent application Ser. No. 12/391,977, entitled “Systems, Methods, andDevices for Isolating Portions of a Wellhead from Fluid Pressure,” filedon Feb. 24, 2009, which is herein incorporated by reference in itsentirety, which claims priority to and benefit of U.S. ProvisionalPatent Application No. 61/031,331, entitled “Systems, Methods, andDevices for Isolating Portions of a Wellhead from Fluid Pressure,” filedon Feb. 25, 2008, which is herein incorporated by reference in itsentirety, and also claims priority to and benefit of U.S. ProvisionalPatent Application No. 61/142,133, entitled “Systems, Methods, andDevices for Isolating Portions of a Wellhead from Fluid Pressure,” filedon Dec. 31, 2008, which is herein incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates generally to devices that couple towellheads. More particularly, the present invention relates to devicesconfigured to isolate portions of wellheads from fluid pressure.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

Wells are frequently used to extract fluids, such as oil, gas, andwater, from subterranean reserves. These fluids, however, are oftenexpensive to extract because they naturally flow relatively slowly tothe well bore. Frequently, a substantial portion of the fluid isseparated from the well by bodies of rock and other solid materials.These solid formations impede fluid flow to the well and tend to reducethe well's rate of production.

This effect, however, can be mitigated with certain well-enhancementtechniques. Well output often can be boosted by hydraulically fracturingthe rock disposed near the bottom of the well, using a process referredto as “fracing.” To frac a well, a fracturing fluid is pumped into thewell fast until the down-hole pressure rises, causing cracks to form inthe surrounding rock. The fracturing fluid flows into the cracks andpropagates them away from the well, toward more distant fluid reserves.To impede the cracks from closing after the fracing pressure is removed,the fracturing fluid typically carries a substance referred to as aproppant. The proppant is typically a solid, permeable material, such assand, that remains the cracks and holds them at least partially openafter the fracturing pressure is released. The resulting porous passagesprovide a lower-resistance path for the extracted fluid to flow to thewell bore, increasing the well's rate of production.

Fracing a well often produces pressures in the well that are greaterthan the pressure-rating of certain well components. For example, somewellheads are rated for pressures up to 5,000 psi, a rating which isoften adequate for pressures naturally arising from the extracted fluid,but some fracing operations can produce pressures that are greater than10,000 psi. Thus, there is a need to protect some well components fromfluid pressure arising from well fracing.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an example of a bypass sleeve inaccordance with an embodiment of the invention;

FIG. 2 is cross-sectional elevation view of the bypass sleeve of FIG. 1;

FIG. 3 is an elevation view of an example of a wellhead assembly adaptedto receive the bypass sleeve of FIG. 1 in accordance with an embodimentof the invention;

FIG. 4 is a cross-sectional elevation view of the wellhead assembly ofFIG. 3;

FIGS. 5-7 illustrate the bypass sleeve of FIG. 1 being prepared forinstallation in the wellhead assembly of FIG. 3;

FIGS. 8-11 illustrate the bypass sleeve of FIG. 1 being installed in thewellhead assembly of FIG. 3;

FIG. 12 illustrates a fracing process in accordance with an embodimentof the invention;

FIG. 13 illustrates the bypass sleeve of FIG. 1 being removed from thewellhead assembly of FIG. 3;

FIG. 14 illustrates a second example of a bypass sleeve in accordancewith an embodiment of the invention;

FIG. 15 illustrates a third example of a bypass sleeve and a wellheadassembly in accordance with an embodiment of the invention;

FIG. 16 illustrates the bypass sleeve of FIG. 15 installed in anotherexample of a wellhead assembly in accordance with an embodiment of theinvention;

FIG. 17 illustrates a fourth example of a bypass sleeve installed in awellhead assembly in accordance with an embodiment of the invention;

FIG. 18 illustrates a pressure barrier coupled to the bypass sleeve ofFIG. 17 in accordance with an embodiment of the invention;

FIGS. 19 and 20 illustrate a fifth example of a bypass sleeve beinginstalled in a wellhead assembly in accordance with an embodiment of theinvention;

FIGS. 21 and 22 illustrate an example of a wellhead adapter inaccordance with an embodiment of the invention;

FIGS. 23-26 illustrate a sixth example of a bypass sleeve in accordancewith an embodiment of the invention;

FIG. 27 illustrates an example of a pressure-barrier adapter inaccordance with an embodiment of the invention;

FIG. 28 illustrates a seventh example of a bypass sleeve in accordancewith an embodiment of the invention;

FIG. 29 illustrates the installation of the bypass sleeve of FIG. 28 andthe pressure-barrier adapter of FIG. 27;

FIG. 30 illustrates a second example of a pressure-barrier adapter inaccordance with an embodiment of the invention;

FIG. 31 illustrates another example of a bypass sleeve and a wellheadassembly in accordance with an embodiment of the invention; and

FIG. 32 illustrates an example of a bypass sleeve, a removable bushing,and a wellhead assembly in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” “said,” and the like, areintended to mean that there are one or more of the elements. The terms“comprising,” “including,” “having,” and the like are intended to beinclusive and mean that there may be additional elements other than thelisted elements. Moreover, the use of “top,” “bottom,” “above,” “below,”and variations of these terms is made for convenience, but does notrequire any particular orientation of the components.

FIGS. 1 and 2 illustrate an example of a bypass sleeve 100. As explainedbelow, the illustrated bypass sleeve 100 couples to a wellhead assemblyand protects components of the wellhead assembly from fluid pressuresthat arise while fracing a well. After describing details of the bypasssleeve 100, an example of a wellhead assembly adapted to receive thebypass sleeve 100 is described with reference to FIGS. 3 and 4.

As illustrated by FIG. 2, the bypass sleeve 100 includes a body 102, alock ring 104, and anti-rotation devices 106 and 108. In thisembodiment, the body 102 has a generally tubular shape that is generallyconcentric about a central axis 110, and the body 102 includes thefollowing features: a bottom edge 112, a lower chamfered surface 114, alower seal assembly 116, a channel 118, an intermediate seal assembly120, an upper a seal assembly 122, a lock-ring receptacle 124, a toolinterface 126, an upper chamfered surface 128, a top edge 130, and aninterior 132 having a pressure-barrier interface 134. In the illustratedembodiment, the bottom edge 112 is generally orthogonal to the centralaxis 110, and the lower chamfered surface 114 is generally defined by asloped bottom corner of the body 102. The body 102 may be made of steelor other appropriate materials.

The illustrated lower seal assembly 116 includes two seal members 136and 138 disposed in grooves 140 and 142. The illustrated channel 118 isa generally tubular recess in the body 102 with edges defined byshoulders 144 and 146. The channel 118 may cooperate with the wellheadassembly described below to generally define a volume around the body102 that is in fluid communication with a valve for, among other things,relieving pressure in the wellhead assembly. The upper shoulder 144functions as a landing surface for axially positioning the bypass sleevein the wellhead assembly, though other features (such as the lowerchamfered surface 114) may serve this purpose in other embodiments. Theillustrated intermediate seal assembly 120 also includes two sealmembers 148 and 150 disposed in two grooves 152 and 154. Similarly, theillustrated upper seal assembly 122 includes two seal members 156 and158 disposed in two grooves 160 and 162.

In the illustrated embodiment, the portion of the body 102 between thechannel 118 and the lock-ring receptacle 124 is the widest portion ofthe body 102, having a diameter 163. To facilitate removal of the bypasssleeve 100 from a wellhead assembly, the widest diameter 163 may besmaller than or generally equal to interior diameters of componentsexpected to be disposed above the bypass sleeve 100 in a wellheadassembly, components such as a blowout preventer, a christmas tree, or afrac tree, as explained below. Thus, in some embodiments, the bypasssleeve 100 is configured to be extracted through other componentsattached to a wellhead. Examples of a wellhead and examples of thesecomponents are described below after describing other features of thebypass sleeve 100.

In the present embodiment, the lock-ring receptacle 124 is a groove inthe body 102 shaped to receive the lock ring 104. The illustratedlock-ring receptacle 124 includes a sloped surface 164 (e.g., conical atleast partially about axis 110), an outer recess (e.g., annular at leastpartially about axis 110) 166, an inner recess (e.g., annular at leastpartially about axis 110) 168, and a rib 170. The outer recess 166 andthe inner recess 168, in this embodiment, are generally parallel to thecentral axis 110, and the rib 170 extends generally perpendicular to thecentral axis 110. As explained below, the lock-ring receptacle 124axially retains the lock ring 104 on the body 102 while allowing thelock ring 104 to expand and contract radially.

The illustrated tool interface 126 includes threads disposed near thetop, external portion of the body 102. In this embodiment, the threadsdefine the widest portion of the body 102 above the rib 170 tofacilitate coupling the body 102 to a tool, as described below withreference to FIG. 6. In other embodiments, the tool interface 126, likethe other threaded interfaces described herein, may include otherstructures configured to couple components, structures such as internalthreads in the interior 132 of the body 102, another lock ring on theinterior or exterior of the body 102, or other biased interlockingmembers, for example. The upper chamfered surface 128 is angled relativeto the central axis 110 to guide the tool toward the tool interface 126,and the illustrated top edge 130 is generally perpendicular to thecentral axis 110.

In the present embodiment, the interior 132 of the body 102 includes atop chamfer 172, the pressure-barrier interface 134, a primary-flowpassage 174, and a bottom chamfer 176. The illustrated pressure-barrierinterface 134 includes threads disposed on an interior sidewall of thebody 102. The threads are disposed in a top portion of the interior 132that has an expanded diameter 178 relative to a diameter 180 of theprimary-flow passage 174.

The primary-flow passage 174 defines a generally right,circular-cylindrical volume that is generally concentric about thecentral axis 110. In some embodiments, the diameter 180 of theprimary-flow passage 174 is generally equal to or larger than minimumdiameters of components disposed down-hole from the bypass sleeve 100,such as a tubing head, a casing hanger, or production casing. Aninterior diameter 180 with this property is believed to facilitate themovement of equipment and fluids between the interior 132 of the body102 and down-hole components, as the diameter of the bypass sleeve 100does not substantially constrain the axial movement of fluids andequipment that pass through other down-hole components. A bypass sleevewith this property is referred to as a “full bore” bypass sleeve.

The illustrated lock ring 104 is generally concentric about the centralaxis 110 and includes a top edge 182, a cam surface (e.g., conical atleast partially about axis 110) 184, a top load shoulder 186, an outersidewall (e.g., annular at least partially about axis 110) 188, achamfer 190, a bottom load shoulder 192, an inner sidewall (e.g.,annular at least partially about axis 110) 194, and a gap 196, which isillustrated by FIG. 1. As illustrated by the cross-section of FIG. 2,the top edge 182 and the load shoulder 192 cooperate with the rib 170and the sloped surface 164 to generally axially restrain the lock ring104 on the body 102. These structures 182, 192, 170, and 164 alsocooperate to guide a radial movement of the lock ring 104 as the lockring 104 is compressed and expanded, as explained below.

In this embodiment, the cam surface 184 is a generally sloped surfacethat generally defines a frusto-conical volume that is generallyconcentric about the central axis 110. The top load shoulder 186 may bea sloped, flat, or curved surface, and it is shaped to interface withcomponents of a wellhead assembly to transmit vertical axial loads,e.g., loads from elevated fluid pressure in the well. These verticalloads may be transmitted between the body 102 and the lock ring 104through the bottom load shoulder 192. Thus, in some embodiments, anupward axial force applied to the body 102 may be transmitted to thelock ring 104 through the bottom load shoulder 192 and to the wellheadassembly through the top load shoulder 186. Similarly, the chamfer 190is configured to interface with components of the wellhead assembly totransmit vertical axial loads directed toward the well between thebypass sleeve 100 and the wellhead assembly, such as the weight of thebypass sleeve 100. The gap 196 is illustrated in FIG. 1. As explainedbelow, the gap 196 allows the lock ring 104 to be compressed radiallyinward into the lock-ring receptacle 124. Other embodiments may includemulti-piece lock rings 104 with more than one gap 196.

The anti-rotation devices 106 and 108 are generally similar or identicaland oriented in opposite directions on the body 102. The illustratedbypass sleeve 100 includes two anti-rotation devices 106 and 108disposed 180° apart at generally the same height on the body 102. Otherembodiments may include more or fewer anti-rotation devices disposed atgenerally the same height or different heights with the same ordifferent angular distributions around the body 102.

Each of the illustrated anti-rotation devices 106 and 108 includes ananti-rotation member 197, a restraining plate 198, a spring 200, and acavity 202 in the body 102. The anti-rotation members 196 may be made ofsteel or other appropriate materials. In this embodiment, theanti-rotation members 196 include top and bottom cam surfaces 204 and206, rotation-reduction surfaces 208 and 210, and a backing plate 212.In this embodiment, the top and bottom cam surfaces 204 and 206 aregenerally flat sloped surfaces, but in other embodiments, they may becurved or have some other shape. The rotation-reduction surfaces 208 and210 in this embodiment are generally flat surfaces that are generallyparallel to the central axis 110 and generally orthogonal to the camsurfaces 204 and 206. The rotation-reduction surfaces 208 and 210 andthe cam surfaces 204 and 206 extend from the backing plate 212, whichhas a generally circular cylindrical shape that is generallycomplementary to the shape of the cavity 202. In some embodiments, thebacking plate 212 may include a tubular sleeve that extends into thecavity 202, overlapping the spring 202, to transmit torque arising fromforces applied to the cam surfaces 204 and 206.

The illustrated spring 202 is a helical compression spring, but in otherembodiments other devices configured to actuate the anti-rotationmembers 196 may be used, for example, a linear motor, a pneumaticdevice, opposing magnets, elastomeric body, or other devices may be usedin place of or in addition to the spring 200. The cavity 202 includes agenerally right circular cylindrical volume that extends generallyperpendicular to the central axis 110 into the body 102 and a recess forreceiving the restraining plate 198. The illustrated restraining plates198 are generally curved to generally match the outer surface of thebody 102 and include an aperture 211. The anti-rotation member 197 mayextend through an aperture 211, and the backing plate 212 may generallyremain on the other side of the restraining plate 198.

In operation, as described below, the anti-rotation devices 106 and 108interface with cavities in a wellhead assembly to prevent or reducerotation of the body 102 relative to the wellhead assembly. Further, asexplained below, the anti-rotation members 196 may recess into thecavity 202 to allow the bypass sleeve 100 to move vertically.

An exemplary wellhead assembly 214 is provided in FIGS. 3 and 4 inaccordance with one embodiment of the present invention. The illustratedwellhead assembly 214 is a surface wellhead, but the present techniqueis not limited to surface applications. Some embodiments may include asubsea tree. The exemplary wellhead assembly 214 includes a casing head216 coupled to a surface casing 218. The wellhead assembly 214 alsoincludes a production casing 220, which may be suspended within thecasing head 216 and the surface casing 218 via a casing hanger 222. Itwill be appreciated that a variety of additional components may becoupled to the casing head 216 to facilitate production from asubterranean well.

For instance, in one embodiment, a tubing head 224 (also referred to asa “tubing spool”) is coupled to the casing head 216. In the presentlyillustrated embodiment, the tubing head 224 is coupled to the casinghead 216 via a union nut 226, which is threaded onto the casing head 216via complementary threaded surfaces 228 and 230. Of course, it will beappreciated that wellhead members, such as the tubing head 224, may becoupled to the casing head 216 in any suitable manner, including throughthe use of various other connectors, collars, or the like. In oneembodiment, the tubing head 224 may be adapted to receive an extendedportion 232 of the casing hanger 222.

A valve assembly 234 is coupled to the exemplary tubing head 224 and mayserve various purposes, including releasing pressure from an internalbore 236 of the tubing head 224. The internal bore 236 of the tubinghead 224 is configured to receive one or more additional wellheadmembers or components, such as the bypass sleeve 100 described above. Aswill be appreciated, operating pressures within the wellhead assembly214 are typically greater during a fracturing process than duringordinary production. In order to protect components of the wellheadassembly 214 having a lower pressure rating (i.e., below the expectedfracturing pressure) from such excessive pressure, the bypass sleeve 100may be introduced within the bore 236 to isolate the portions of thewellhead assembly 214 from at least some of this pressure.

The exemplary tubing head 224 includes a sloped landing surface 238configured to abut the shoulder 144 of the bypass sleeve 100 (FIG. 2).In some embodiments, these structures 144 and 238 cooperate to axiallyposition the bypass sleeve 100 in the wellhead assembly 214, asexplained below. The exemplary tubing head 224 also includes a flange240 configured to facilitate coupling of various components or wellheadmembers.

The exemplary wellhead assembly 214 includes various seals 242 toisolate pressures within different sections of the wellhead assembly214. For instance, as illustrated, such seals 242 include seals disposedbetween the casing head 216 and the casing hanger 222 and between thecasing hanger 222 and the tubing head 224. Further, various componentsof the wellhead assembly 214, such as the tubing head 224, may includeinternal passageways 244 that allow testing of one or more of the seals242. When not being used for such testing, these internal passageways244 may be sealed from the exterior via pressure barriers 246.

The illustrated wellhead assembly 214 also includes an adapter 248 and ablow-out preventer 250. The adapter 248 couples to the tubing head 224via the flange 240. In this embodiment, the adapter 248 includes alock-ring receptacle 252 and anti-rotation interfaces 254. Theillustrated lock-ring receptacle 252 is a generally circular groove thatis generally complementary to the lock ring 104. In this embodiment, theanti-rotation interfaces 254 are recesses that are generallycomplementary to the anti-rotation members 197 of FIGS. 1 and 2.

The illustrated blowout preventer 250 couples to the wellhead assembly214 via the adapter 248. The blowout preventer 250 includes a valve anda valve actuator, such as a hydraulic actuator, configured to close thevalve. The blowout preventer 250 is configured to close the bore 236 ifthe pressure in the bore 236 exceeds some threshold condition. In otherembodiments, other devices may be connected to the flange 240 or theadapter 248. For example, a christmas tree or a frac tree may beconnected to one of these components.

FIGS. 5-11 illustrate steps in a process for installing the bypasssleeve 100 of FIG. 1 in the wellhead assembly 214 of FIG. 3. Asillustrated by FIG. 5, a pressure barrier 255 is initially installed inthe bypass sleeve 100. The illustrated pressure barrier 255 is threadedinto the thread interface 134 of the bypass sleeve 100, but in otherembodiments, these components 255 and 100 may be joined with othertechniques. In some embodiments, the pressure barrier 255 is a checkvalve configured to obstruct fluid flowing out of the well, or in otherembodiments, the pressure barrier 255 is a member that obstructs fluidsflowing in both directions.

FIG. 5 also illustrates a tool 256 proximate the bypass sleeve 100. Thetool 256 couples to the bypass sleeve 100 via the tool interface 126, asillustrated by FIG. 6. The tool 256 rotates relative to the bypasssleeve 100, as illustrated by arrow 258 in FIG. 5, and translates alongthe central axis 110, as illustrated by arrow 260 in FIG. 6. Theillustrated tool 256 includes a tubular distal portion 262 that is sizedto overlap the rib 170. As the tool 256 translates, a contact surface264 at the end of the distal portion 262 contacts the cam surface 184 ofthe lock ring 104. The contact surface 264 slides along the cam surface184 and compresses the lock ring 104 radially inward, as illustrated byarrow 266, until the lock ring 104 is in the contracted positionillustrated by FIG. 7 and the lock ring 104 is partially orsubstantially entirely recessed into the lock-ring receptacle 124. Asthe lock ring 104 contracts generally radially inward, the gap 196illustrated in FIG. 5 decreases and the lock ring 104 is biased.

Next, the bypass sleeve 100 may be positioned in the wellhead assembly214, as illustrated by FIG. 8. The tool 256 lowers the bypass sleeve 100into the wellhead assembly 214 through the blowout preventer 250 and theadapter 248. The lock ring 104 remains in the compressed positionillustrated by FIG. 7 while the bypass sleeve 100 is lowered into thewellhead assembly 214. To accommodate features in the wellhead assembly214 that are narrower than the distal portions of the anti-rotationdevices 106 and 108, the anti-rotation members 197 may partially orsubstantially entirely recessed into the cavities 202, compressing thespring 200. The movement of these components is described further belowwith reference to FIGS. 9, 10, and 12. In some embodiments, the tool 256lowers the bypass sleeve 100 until the shoulder 144 of the bypass sleeve100 contacts the sloped landing surface 238 of the tubing head 224. Theheight of these features 144 and 238 position the anti-rotation devices106 and 108 at generally the same height as the anti-rotation interfaces254, and the lock ring 104 may be positioned at generally the sameheight as the lock-ring receptacle 252 in the adapter 248.

While the anti-rotation devices 106 and 108 are generally axiallyaligned with the anti-rotation interfaces 254, these features may not berotationally aligned, as illustrated by FIG. 9. As mentioned above, theanti-rotation members 197 recessed into the cavity 202, compressing thespring 200 to accommodate features of the wellhead assembly 214. Toimpede rotation of the bypass sleeve 100 relative to the wellheadassembly 214, the anti-rotation devices 106 and 108 engage theanti-rotation interfaces 254 in the adapter 248. If the bypass adapter100 begins to rotate within the wellhead assembly 214, as might occurwhen disengaging the tool 256, at some point within 180° of rotation,the anti-rotation devices 106 and 108 will engage the anti-rotationinterfaces 254 and impede further rotation. Rotation of the bypasssleeve 100 is illustrated by arrow 268 in FIG. 9, and the anti-rotationdevices 106 and 108 are illustrated in the disengaged position in FIG.9.

FIG. 10 illustrates the anti-rotation devices 106 and 108 in the engagedposition. As the bypass sleeve 100 rotates, eventually the anti-rotationmembers 197 align with the anti-rotation interfaces 254. When they arealigned, the anti-rotation members 197 are driven into the anti-rotationinterfaces 254 by the springs 200. In some embodiments, theanti-rotation members 197 may be characterized as having a single degreeof freedom relative to the bypass sleeve 100. Once engaged, therotation-reduction surfaces 208 and 210 may receive forces from thevertical surfaces of the anti-rotation interfaces 254 that producedtorques tending to counteract rotation of the bypass sleeve 100.

Other embodiments may omit the anti-rotation devices 106 and 108 or theymay include other in types of anti-rotation devices. For example, insome embodiments, the anti-rotation devices 106 and 108 may be disposedon the adapter 248 and the anti-rotation interfaces 254 may be disposedon the bypass sleeve 100. In some embodiments, a friction member similarto a drum break may interface between the bypass sleeve 100 and othercomponents of the wellhead assembly 214 to reduce rotation. Theillustrated anti-rotation devices 108 and 106 include components thattranslate generally radially. Other embodiments may include members totranslate generally axially. For example, the anti-rotation members 106and 108 may be disposed near the bottom edge 112 (FIG. 2), and theanti-rotation members 197 may translate axially downward to engage ananti-rotation interface in the tubing head 224.

The anti-rotation devices 106 and 108 are believed to facilitate removalof the tool 256 and the pressure barrier 255 (FIG. 5) from the bypasssleeve 100. As explained above, the tool 256 and the pressure barrier255 engage the bypass sleeve 100, in some embodiments, through threadedcouplings. Thus, to disengage these components, they are typicallyrotated relative to one another. The anti-rotation devices 106 and 108tend to prevent the bypass sleeve 100 from rotating with the tool 256,thereby facilitating relative rotation in some embodiments.

FIG. 11 illustrates the bypass sleeve 100 in the installed position. Tocomplete installation and position the bypass sleeve 100 as illustratedby FIG. 11, the tool 256 (FIG. 8) is rotated relative to the bypasssleeve 100. As the tool 256 rotates, the distal portion 262 (FIG. 7)translates axially away from the lock ring 104, and the lock ring 104expands radially into the lock-ring receptacle 252. The lock-ringreceptacle 252 includes upper and lower shoulders 270 and 272 thatimpede the bypass sleeve 100 from the translating axially. In someembodiments, the lock ring 104 is not completely relaxed and is biasedradially inward by the lock-ring receptacle 252.

The installation process illustrated by FIGS. 5-11 is the first step inan example of a process 274 for fracing a well illustrated by FIG. 12.In this figure, the process for installing the bypass sleeve isillustrated by box 276. After installing the bypass sleeve, the blowoutpreventer 250 is removed from the wellhead assembly 214, as illustratedby block 278. As noted above, the pressure barrier 255 generally sealsto the bypass sleeve 100, and the bypass sleeve 100 generally seals tothe tubing head 224. As a result, in some embodiments, the well isgenerally sealed while removing the blowout preventer 250.

Next, a frac tree or other frac-related equipment is coupled to thewellhead assembly 214, as illustrated by block 280. In some embodiments,this step includes coupling tracking equipment to the flange 240 of thewellhead assembly 214 illustrated in FIG. 4. As will be appreciated, thefrac tree may include valves or caps that tend to confine pressure inthe wellhead assembly 214 above the pressure barrier 255. Next, thepressure barrier 255 is removed from the bypass sleeve 100, asillustrated by block 282. Removing the pressure barrier 255 may includepassing another tool through the frac tree and unthreading or otherwisedisengaging the pressure barrier 255 from the bypass sleeve 100. Duringthis step, in embodiments incorporating the embodiment of FIG. 2, theanti-rotation devices 106 and 108 may again prevent the bypass sleeve100 from rotating with the pressure barrier 255.

After removing the pressure barrier 255, the frac equipment is in fluidcommunication with the production casing 220, and the well is fraced, asillustrated by block 284. As described above, fracing includes pumping afluid into the well at a rate sufficient to elevate down-hole pressuresand fracture subterranean rock formations. This act may be aided byfeatures of the bypass sleeve 100 described above with reference to FIG.2, inter alia. Because the inner diameter 180 of the bypass sleeve 100is greater than or generally equal to the diameter of the productioncasing 220, in some embodiments, the fracing fluid is believed to have arelatively unobstructed flow path into the well. During this step, thebypass sleeve 100 protects portions of the wellhead assembly fromfracing pressures, which may be greater than 5000 psi, 10,000 psi,15,000 psi, or larger. In some embodiments, the bypass sleeve 100protects portions of the wellhead assembly 214 of FIG. 8, e.g., thetubing head 224 or the joint between the adapter 248 and the flange 240.

After fracing the well, the pressure barrier 255 is reinstalled in thebypass sleeve 100, as illustrated by block 286. In some embodiments,reinstalling the pressure barrier 255 includes passing the pressurebarrier 255 through the frac tree with one of the tools described aboveand threading or otherwise coupling the pressure barrier 255 to thebypass sleeve 100. Next, of the frac tree is removed, as illustrated byblock 288, and the blowout preventer 250 or a christmas tree isreinstalled on the wellhead assembly 214, as illustrated by block 290.

Finally, the bypass sleeve 100 is removed along with the pressurebarrier 255, as illustrated by block 292. One way in which this step isperformed is illustrated by FIG. 13. In this embodiment, the tool 256 isthreaded back onto the bypass sleeve 100 while the anti-rotation devices106 and 108 impede the bypass sleeve 100 from rotating with the tool256. As the tool 256 threads on to the bypass sleeve 100, the tool 256returns the lock ring 104 to the compressed position, as described abovewith reference to FIG. 6, thereby disengaging the lock ring 104 from thelock-ring receptacle 252.

Once the lock ring 104 is returned to the compressed position, the tool256 is pulled generally axially upward along with the bypass sleeve 100,as illustrated by arrow 294. The upward movement of the anti-rotationdevices 106 and 108 biases the anti-rotation members 197 against theanti-rotation interfaces 254, and the resulting force against the topcam surfaces 204 recesses the anti-rotation members 197 in the cavity202, compressing the springs 200, as illustrated by arrows 296.Retracting the anti-rotation members 197 allows the bypass sleeve 100 totranslate back through the blowout preventer 250 and exit the wellheadassembly 214.

During some embodiments of the fracing process 274 described above withreference to FIG. 12, the bypass sleeve 100 and the pressure barrier 255are installed generally simultaneously and are removed generallysimultaneously, e.g., in a single trip of the tool 256 into the wellheadassembly 214. One-trip installation and one-trip removal of the bypasssleeve 100 and pressure barrier 255 is believed to speed the fracingprocess 274 relative to fracing processes in which the pressure barrier255 and the bypass sleeve 100 are installed in separate trips.

Further, during execution of some embodiments of the fracing process274, the wellhead assembly 214 has a device installed that is adapted tocontain fluid in the well while the blowout preventer 250 is removed.The pressure barrier 255 confines fluid to the well during portions ofthe fracing process 274, e.g., when the fracing tree or the blowoutpreventer 250 are not installed. This is believed to reduce blowouts.

The bypass sleeve 100 described above with reference to FIGS. 1 and 2has an integrated sleeve restraint, i.e., the lock ring 104 andlock-ring receptacle 124, but other embodiments may include anon-integrated sleeve restraint. An example of such an embodiment isillustrated by FIG. 14, which depicts a bypass sleeve 304 and a separatesleeve restraint 302.

The sleeve restraint 302 and the bypass sleeve 304 include many of thesame features as the bypass sleeve 100 described above. Accordingly, inthe interest of the economy, the features that are similar areidentified with the same reference number as was used above. Further,the bypass sleeve 304 is installed in a wellhead assembly 300 thatincludes many of the features of the wellhead assembly 214 describedabove with reference to FIG. 4, so the same reference numbers are usedto identify features that are generally similar between the wellheadassemblies 214 and 300. This convention is followed throughout thewritten description.

The illustrated bypass sleeve 304 is impeded from axial-upward movementthrough the wellhead assembly 300 by the sleeve restraint 302. In thisembodiment, the sleeve restraint 302 includes the previously-describedlock ring 104, anti-rotation devices 106 and 108, lock-ring receptacle124, tool interface 126, and many of the other features disposed nearthe top of the previously-described bypass sleeve 100 (FIG. 2). In theillustrated embodiment, the sleeve restraint 302 does not include thepressure-barrier interface 134, as this feature is disposed in thebypass sleeve 304. In other embodiments, the pressure-barrier interface134 may be disposed partially or entirely in the sleeve restraint 302.To allow the pressure barrier 255 to reach the pressure-barrierinterface 134, in some embodiments, the sleeve restraint 302 has adiameter 306 (e.g., a minimum diameter) that is larger than a diameter308 of the pressure barrier 255.

The sleeve restraint 302 is shown in FIG. 14 in a split view, with eachhalf depicting different stages of the sleeve restraint 302 interfacingwith the tool 256. In the right portion of FIG. 14, the tool 256 isshown in a partially-retracted position, leaving the lock ring 104 inthe expanded position, and in the left portion of FIG. 14, the tool 256′is shown in a fully-engaged position, compressing the lock ring 104 inthe contracted position.

In this embodiment, the bottom portion of the sleeve restraint 302includes a flange 310 that overlaps part of the bypass sleeve 304. Theillustrated flange 310 is generally concentric about the central axisand generally has a tubular shape. The flange 310 includes a sealingmember 312 disposed in a groove 314 in an inner surface of the flange310. The flange 310 also includes a chamfered surface 316 that engageswith lock pins that are described further below along with other detailsof the wellhead assembly 300.

The bypass sleeve 304 of the present embodiment includes a tubing-headinterface 318, the pressure-barrier interface 134, another toolinterface 320, and a flange 322 that overlaps and seals against the sealmember 312 on the flange 310. The illustrated tubing-head interface 318is a chamfered surface that is positioned to contact subsequentlydescribed locking pins in the wellhead assembly 300. In this embodiment,the tool interface 320 is a threaded inner surface of the bypass sleeve304 with a diameter that is smaller than the diameter 306 of the sleeverestraint 302.

The illustrated wellhead assembly 300 includes locking pins 324 that arepositioned to apply a force to the tubing-head interface 318. Thelocking pins 324 extend generally radially through the flange 240 in thetubing head 224. The illustrated locking pins 324 are threaded to twobushings 326 that are threaded to the flange 240. In this embodiment,the locking pins 324 include a chamfered tip 328 that contacts both thetubing-head interface 318 on the bypass sleeve 304 and the chamferedsurface 316 on the sleeve restraint 302. The locking pins 324 maycooperate with the sleeve restraint 302 to hold the bypass sleeve 304.

In operation, the bypass sleeve 304 may be installed in the wellheadassembly 300 with a single trip or with two trips. For example, a toolwith exterior threads configured to interface with the tool interface320 may lower the bypass sleeve 304 and the pressure barrier 255 intothe wellhead assembly 300, and then in a separate trip, the tool 256 maylower and install the sleeve restraint 302, using an installationprocess similar to that described above with reference to the bypasssleeve 100 of FIG. 2. In other embodiments, the sleeve restraint 302 andthe bypass sleeve 304 may be installed while connected together in asingle trip.

Once the bypass sleeve 304 is positioned in the wellhead assembly 300,the bushings 326 are rotated to drive the locking pins 324 radiallyinward, biasing the chamfered tip 328 against the tubing-head interface318 and holding the bypass sleeve 304 in the wellhead assembly 300. Thesleeve restraint 302 may interface with the adapter 248 to impede thebypass sleeve 304 from moving axially upward and the seals on the sleeverestraint 302 may protect the locking pins 324 from fracing pressures.In some embodiments, the sleeve restraint 302 may serve primarily toprotect the locking pins 324 from this pressure, or in otherembodiments, the sleeve restraint 302 may serve primarily to restrainthe bypass sleeve 304, allowing the locking pins 324 to be omitted(which, like other express opportunities for omissions identifiedherein, is not to suggest that other features may not also be omitted).

In some embodiments, the bypass sleeve 304 functions without the sleeverestraint 302, as illustrated by FIG. 15. In this embodiment, theadapter 248 is omitted, but in other embodiments, the adapter 248 may beincluded between the flange 240 and the blowout preventer 250. Theillustrated bypass sleeve 304 does not extend above the top 330 of thetubing head 224, into the blowout preventer 250 or other componentscoupled to the flange 240, but in other embodiments, the sleeve 304 mayextend above the flange 240.

FIG. 16 illustrates another embodiment in which the bypass sleeve 304functions without the sleeve restraint 302. This embodiment includes thebypass sleeve 304 installed in another example of a wellhead assembly332. The illustrated wellhead assembly 332 is generally similar to thewellhead assembly 300 described above except that the illustratedwellhead assembly 332 includes an adapter 334 with a flange 336 thatseals against the bypass sleeve 304. The flange 336 extends below thetop 330 of the tubing head 224 and includes a seal member 338 disposedin a groove 340. The illustrated seal member 338 and groove 340 aredisposed in an inner surface of the flange 336 and are positioned toseal against the outer surface of the bypass sleeve 304.

The adapter 334 has an inner diameter 342 that is generally narrowerthan an outer diameter 344 of the bypass sleeve 304 such that theadapter 334 overlaps the bypass sleeve 304. Consequently, to install thebypass sleeve 304 in some embodiments, the adapter 334 is removed whilethe bypass sleeve 304 is installed in the wellhead assembly 332. Forexample, in some installation processes, the bypass sleeve 304 isinstalled through the previously-described adapter 248 and, then, theadapter 248 is replaced with the adapter 334 to provide added supportand sealing during a fracing operation. After fracing the well, andsealing the bypass sleeve 304 with the previously-described pressurebarrier 255, the adapter 334 may again be replaced with the adapter 248to allow the bypass sleeve 304 to be withdrawn through a blowoutpreventer, christmas tree, or other equipment attached to the wellheadassembly 332.

FIG. 17 illustrates another example of a bypass sleeve 346 installed inanother embodiment of a wellhead assembly 348. Again, many of thefeatures of these components 346 and 348 are similar to the features ofcomponents described above. Accordingly, the same reference numbers areused to indicate features that are generally similar to features thatwere described above with the same reference numbers.

The bypass sleeve 346 includes exterior threads 350 that are configuredto secure the bypass sleeve 346 in the wellhead assembly 348. In thisembodiment, the threads 350 have a wider outer diameter 352 thanportions of the bypass sleeve 346 disposed above and below the threads350. This is believed to facilitate moving the bypass sleeve 346 intoand out of the wellhead assembly 348 without the threads 350 orcomplementary structures interfering with components disposed above orbelow the threads 350. In other embodiments, portions of the bypasssleeve 346 disposed above the threads 350 may be wider than the diameterof the threads 350.

The wellhead assembly 348 illustrated by FIG. 17 includes an adapter 354configured to interface with the bypass sleeve 346. In this embodiment,the adapter 354 includes complimentary threads 356 that join to thethreads 350. The adapter 354 also includes a lower portion 358 with anarrower diameter to provide a sealing surface for the upper sealassembly 122.

In operation, the bypass sleeve 346 is installed in the wellheadassembly 348 with a process similar to the process 274 described abovewith reference to FIG. 12. To install the bypass sleeve 346, thepressure barrier 255 is threaded to the pressure-barrier interface 134,and the tool 256 (shown above in FIG. 6, inter alia) is coupled to thetool interface 126. Then, the bypass sleeve 346 and the pressure-barrierinterface 134 are lowered into the wellhead assembly 348 through theblowout preventer 250, and the tool 256 rotates the bypass sleeve 346 toengage the exterior threads 350 and the threads 356. In someembodiments, the tool interface 126 is threaded in the same direction(e.g., clockwise or counter clockwise) as the exterior threads 350, suchthat torque from tightening the bypass sleeve 346 against the adapter354 also tends to tighten the tool 256 against the bypass sleeve 346.

A variety of techniques may be used to disengage the tool 256 withoutalso disengaging the bypass sleeve 346 from the adapter 354. Forexample, the locking pins 324 may be temporarily or permanently engagedwith the bypass sleeve 346 to impede the bypass sleeve 346 from rotatingwhen the tool 256 unthreads. To this end, in some embodiments, thebypass sleeve 346 includes dimples in its outer surface near the pins324 to provide an engagement surface for the pins 324 to apply a torqueto the bypass sleeve 346, thereby tending to reduce undesired rotationof the bypass sleeve 346. A similar technique may be used when removingor installing the pressure barrier 255 (shown above in FIG. 6). Inanother example, the tool interface 126 is threaded in an oppositedirection from the direction of the outer threads 350, and the tool 256is coupled to the bypass sleeve 346 by both threads and a shear pin. Inthis embodiment, once the bypass sleeve 346 is engaged with the adapter354, the torque counteracting further rotation of the bypass sleeve 346shears the shear pin, and the tool 256 unthreads from the bypass sleeve346 by continuing to rotate in the same direction without the shear pinpreventing relative rotation of the tool 256 and the bypass sleeve 346.

FIG. 18 illustrates an example of an intermediary member connecting thepressure barrier 255 to the bypass sleeve 346. The illustratedpressure-barrier adapter 360 includes a flange 362 having a threadedinterface 364 that is complementary to the tool interface 126 on theexterior of the bypass sleeve 346. The pressure-barrier adapter 360further includes a secondary tool interface 366 that is configured tointerface with the tool 256 discussed above with reference to FIG. 6.The pressure-barrier adapter 360 also includes a pressure-barrierinterface 368 that is configured to secure the pressure barrier 255 inan interior 370 of the pressure-barrier adapter 360.

In operation, the pressure-barrier adapter 360 may be installed andremoved with the pressure barrier 255. The assembly of the bypass sleeve346, the pressure-barrier adapter 360 and the pressure barrier 255 isintroduced into the wellhead assembly 348 with a process similar to theprocesses of installing the bypass sleeve 346 described above withreference to FIG. 17. The pressure-barrier adapter 360 and pressurebarrier 255 are threaded to the tool interface 126 of the bypass sleeve346 outside of the wellhead assembly 348, and then, the resultingassembly is placed in the wellhead assembly 348 through the blowoutpreventer 250 by coupling the tool 256 to the tool interface 366 on thepressure-barrier adapter 360. In some embodiments, the threads on thesecondary tool interface 366, the tool interface 126, and the exteriorthreads 350 are threaded in the same direction, such that installationof the bypass sleeve 346 via the pressure-barrier adapter 360 does nottend to unthread the pressure-barrier adapter 360 from the bypass sleeve346. Then, before fracing the well, the pressure barrier 255 is removedfrom the wellhead assembly 348 with the pressure-barrier adapter 360. Toremove these components, a different tool with a wider interior diameterand oppositely threaded flange is engaged with the tertiary toolinterface 369. Then, the second tool rotates the pressure-barrieradapter 360 to disengage the pressure-barrier adapter 360 from thebypass sleeve 346. To prevent the bypass sleeve 346 from rotating whendisengaging the pressure-barrier adapter 360, the locking pins 324 maybe engaged against the side of the bypass sleeve 346. Because thetertiary tool interface 369 is oppositely threaded relative to the toolinterface 126, tightening the second tool against the pressure-barrieradapter 360 tends to disengage the pressure-barrier adapter 360 from thebypass sleeve 346. Once the bypass sleeve 346 and intermediary memberare separated, the pressure-barrier adapter 360 and the pressure barrier255 are removed from the wellhead assembly 348. To reattach the pressurebarrier 255 after fracing, the second tool is re-attached to thetertiary tool interface 369 and a shear pin is placed through thesecomponents to impede relative rotation. Then, the pressure-barrieradapter 360 and pressure barrier 255 are placed in the wellhead assembly348 and threaded to the tool interface 126 until the shear pin issheared and the second tool unthreads.

FIGS. 19-20 illustrate another example of an adapter 370, a bypasssleeve 372, and a wellhead assembly 374. In this embodiment, the adapter370 includes sleeve restraints 376. The sleeve restraints 376 include anactuator 378 and a sliding member 380. In some embodiments, the actuator378 is a hydraulic actuator, a spring-driven actuator, a linear motor, ascrew drive, or a manually-operated actuator configured to displace thesliding member 380. The sliding member 380 is generally complementary toa cavity 382 in the adapter 370 such that the sliding member 380 can beretracted into the cavity 382 by the actuator 378, as illustrated byFIG. 19. The bypass sleeve 372 includes the features of the bypasssleeve 304 described above with reference to FIG. 15, except that insome embodiments its top edge 384 is generally flat near its outerdiameter to interface with the sliding member 380.

The operation of the sleeve restraints 376 is illustrated by FIG. 20.The bypass sleeve 372 is positioned in the wellhead assembly 374 usingthe process for installing the previously-described bypass sleeve 304 inFIG. 15. Then, the sleeve restraints 376 lock the bypass sleeve 372 inplace. The actuators 378 drive the sliding members 380 radially inwarduntil the sliding members 380 overlap the top 384 of the bypass sleeve372, thereby generally confining the bypass sleeve 372 in the wellheadassembly 374. To remove the bypass sleeve 372, the movement of thesliding members 380 is reversed with the actuator 378, and the slidingmembers 380 retract into the cavity 382 of the adapter 370.

FIG. 21 illustrates another example of an adapter 386 and sleeverestraints 388 that may be used in the wellhead assembly 374 with thebypass sleeve 372. The illustrated adapter 386 includes a generallyannular cavity 390. The sleeve restraint 388 includes a lock ring 392that generally has a C-shape and an actuator 394 connected to the ends396 and 398 of the lock ring 392. The adapter 386 may be installed inthe wellhead assembly 348 in place of the adapter 370.

The operation of the adapter 386 is illustrated by FIG. 22. After thebypass sleeve 372 is positioned in the wellhead assembly 374 (asillustrated in FIGS. 19 and 20), the actuator 394 drives the ends 396and 398 of the lock ring 392 toward each other, as illustrated by arrows400 in FIG. 22, thereby contracting the lock ring 392 and drawing thelock ring 392 out of the cavity 390. In some embodiments, thecontraction of the lock ring 392 causes the lock ring 392 to overlap thetop 384 of the bypass sleeve 372, thereby restraining the bypass sleeve372 in the wellhead assembly 374. To remove the bypass sleeve 372, themovement of the actuator 394 is reversed, and the ring 392 is expandedback into the cavity 390 of the adapter 386.

FIGS. 23-27 illustrate another example of a bypass sleeve 402. Asillustrated by FIGS. 23 and 24, the bypass sleeve 402 includes a body404, a lower seal member 406, an intermediate seal member 408, and anupper seal assembly 410.

As illustrated by FIG. 24, the illustrated body 404 is generallyconcentric about a central axis 412 and includes grooves 414 and 416, achannel 418, a sleeve restraint 420, and a compression-seal interface422. The grooves 414 and 416 are shaped to receive the lower seal member406 and the intermediate seal member 408, respectively. The channel 418is bounded by shoulders 424 and 426. The illustrated sleeve restraint420 includes external threads on the body 404, but in other embodiments,the sleeve restraint 420 may include other structures configured torestrain the sleeve in a wellhead assembly. In this embodiment, thethreads extend further radially outward from the body 404 than the sealmembers 406 and 408, such that these seal members 406 and 408 tend tonot interfere with threads that are sized to engage the sleeve restraint420, i.e., the seal members 406 and 408 have a smaller diameter than thethreads on the sleeve restraint 420. In some embodiments, the sleeverestraint 420 has a larger diameter than all, or substantially all, ofthe bypass sleeve 402 disposed below the sleeve restraint 420.

The compression seal interface 422 includes a shelf 428, threads 430, agroove 432, and shear-pin apertures 434. The shelf 428 may be generallyorthogonal to the central axis 412, or it may be sloped or curved. Inthis embodiment, the threads 430 are threaded in the same direction asthe threads on the sleeve restraint 420, but in other embodiments, theymay be threaded in opposite directions. The groove 432 is generallyconcentric about the central axis 412 and is shaped to allow componentsof the upper seal assembly 410 to translate axially within the confinesof an axial range and also rotate, as explained below. The shear-pinapertures 434 extend generally radially into the body 404 and are shapedto receive a portion of a subsequently described shear pin.

As illustrated by FIG. 24, the upper seal assembly 410 includes abushing 436, a washer 438, and a compression-seal member 440. In thisembodiment, the bushing 436 has a generally tubular shape and isgenerally concentric about the central axis 412. The bushing 436 may bemade of steel or other appropriate materials. The illustrated bushing436 includes a top chamfer 442, a tool interface 444, shear pins 446,shear-pin apertures 447, guide members 448, threads 450, and a bottomface 452. The illustrated tool interface 444 is formed from twogenerally-circular apertures through the bushing 436 that are disposednear the top of the bushing 436. In other embodiments, the toolinterface 444 may have another shape, such as threads, slots, orstructures shaped to interface with a lock ring.

In the illustrated embodiment, the shear pins 446 extended generallyradially inward from the shear-pin apertures 447. The shear pins 446 maybe made of metal, plastic, ceramic, or other appropriate materials. Asexplained below, the shear pins 446 shear when a torque above somethreshold is applied to the bushing 436. Accordingly, the shape andmaterial of the shear pins 446 may be selected with a desired torquethreshold in mind. In some embodiments, the shear pins 446 arereplaceable.

The illustrated guide members 448 extend generally radially inward intothe bushing 436. In this embodiment, the guide members 448 are twogenerally right-circular-cylindrical members generally disposed 180degrees apart, but in other embodiments, they may have other shapes orinclude a different number of structures. For example, in oneembodiment, the guide members 448 are formed by a single rib extendinggenerally radially inward and generally concentric about the centralaxis 412. The threads 450 are complementary to the threads 430 on thebody 404. The bottom face 452 may be generally flat and generallyorthogonal to the central axis 412.

The illustrated washer 438 is shaped to function as an interface betweenthe bottom face 452 of the bushing 436 and the compression-seal member440. Accordingly, in some embodiments, the washer 438 is made of metalor some other material selected to protect the compression-seal member440 from sliding friction while transmitting an axial load from thebushing 436 to the compression-seal member 440. The bottom face of thewasher 438 is generally flat and generally orthogonal to the centralaxis 412, but in other embodiments, it may be sloped or curved.

The illustrated compression-seal member 440 is a compressible material,such as an elastomer, that has a Poisson's ratio greater than 0, e.g.,greater than 0.25, 0.35 or 0.4, such that an axial load causes thecompression-seal member 440 to expand radially and bias against awellhead assembly. The compression-seal member 440 may have a generallyrectangular cross-section, or it may have an angled or curved face orfaces shaped to enhance radial movement, e.g., a wedge shape.

FIGS. 25 and 26 are cross-sectional views that illustrate the bypasssleeve 402 before and after installation, respectively. As illustratedby FIG. 25, before installation, the shear pins 446 cooperate with thethreads 450 and 430 to couple the bushing 436 to the body 404, e.g.,with generally zero degrees of freedom. The threads 430 and 450 tend tolimit axial movement of the bushing 436 relative to the body 404, andthe shear pins 446, extending through the shear-pin apertures 447 intothe shear-pin apertures 434, generally tend to limit both relativerotation of the bushing 436 and the body 404 and axial movement. In thisembodiment, there is a gap 454 between the bottom face 452 of thebushing 436 and the washer 438. In other embodiments, the gap 454 may beclosed, and the bottom face 452 may contact the washer 438 withoutsubstantially biasing the compression-seal member 440 beforeinstallation. The guide members 448 extend into the groove 432 near atop portion of the groove 432, leaving a gap 456 that, in someembodiments, is larger than the gap 454.

FIG. 26 illustrates the bypass sleeve 402 installed in a wellheadassembly 458. The illustrated wellhead assembly 458 includes the blowoutpreventer 250, an adapter 460 and the tubing head 224. The illustratedadapter 460 includes threads 462 that are complementary to the threads420 on the body 404.

In the illustrated embodiment, the bypass sleeve 402 is installed in thewellhead assembly 458 with a two-step process. First, the bypass sleeve402 is threaded onto the adapter 460. To this end, a tool may couple tothe tool interface 444 and lower the bypass sleeve 402 through theblowout preventer 250. (One example of a tool configured to interfacewith the bypass sleeve 402 is described below with reference to FIG.29.) When the bypass sleeve 402 reaches the threads 462, the toolrotates the bypass sleeve 402 to engage the threads 420 with the threads462. While engaging the threads 420 and 462, the shear pins 446 remainin an un-sheared state, as illustrated by FIG. 25. Torque applied by thetool to the bushing 436 is transferred to the body 404 through the shearpins 446, thereby causing the body 404 to rotate and couple to thewellhead assembly 458.

When the threads 420 and 462 are substantially or fully engaged, thetubing head 224 impedes further axial movement of the body 404, therebycounteracting the tendency of the threads 420 and 462 to axially movethe body 404 and creating a torque that counteracts the rotation of thetool. Despite this counter-rotation torque, the tool continues torotate, elevating shear in the shear pins 446 until the shear pins 446fracture into separate pieces 446′ and 446″, as illustrated by FIG. 26.

When the shear pins 446 fracture, in this embodiment, they generallycease transmitting torque between the body 404 and the bushing 436,which allows the bushing 436 to rotate relative to the body 404. At thisstage, the bushing 436 may be characterized as having one or two degreesof freedom relative to the body 404, depending on whether the threads430 and 450 are engaged. Rotation and downward movement of the bushing436 engages (or further engages) the threads 430 and 450, and thebushing 436 translates axially toward the compression-seal members 440,closing the gap 454. Axial movement of the bushing 436 is relativelyunimpeded by the guide members 448 within a range defined by the grooves432. After sufficient axial movement, the bottom face 452 of the bushing436 biases, e.g., compresses, the washer 438 against thecompression-seal member 440. The shoulder 428 counteracts this force,axially biasing the compression-seal member 440. As the compression-sealmember 440 is biased, it expands radially outward, as illustrated byarrows 464, and compresses against the sidewalls of the adapter 460,sealing the upper portion of the adapter 460.

The bypass sleeve 402 may also be removed through the blowout preventer250 (or other equipment coupled to the tubing head 224). To remove thebypass sleeve 402, the tool is lowered through the blowout preventer 250and engaged to the tool interface 444. Then, the tool rotates thebushing 436 in the opposite direction from the direction it was rotatedduring installation. As of the bushing 436 rotates, the threads 430 and450 cause the bushing 436 to translate axially upward. Upward axialmovement of the bushing 436, however, is constrained by the guide member448 and the groove 432. When the guide member 448 reach the top of thegroove 432, axial movement of the bushing 436 relative to the body 404is impeded by contact between the guide member 448 and the top of thegroove 432, and the body 404 begins to rotate with the bushing 436. Thisrotation of the body 404 disengages the threads 420 and 462, and thebypass sleeve 402 is freed from the adapter 460, at which point the toolextracts the bypass sleeve 402 through the blowout preventer 250.

FIG. 27 illustrates additional details of the wellhead assembly 458. Asillustrated, the bypass sleeve 402 is installed in the wellhead assembly458 along with a pressure-barrier adapter 466. The illustratedpressure-barrier adapter 466 is a generally tubular member that includesseals 468 and 470 disposed in grooves 472 and 474, and apressure-barrier interface 476. The illustrated pressure-barrierinterface 476 is formed by threads in the interior of thepressure-barrier adapter 466. In some embodiments, the threads on thepressure-barrier interface 476 are threaded in an opposite directionfrom the threads 420 on the bypass sleeve 402, or in other embodiments,they are threaded in the same direction. The pressure-barrier interface476 is configured to secure a pressure barrier to the pressure-barrieradapter 466.

The pressure-barrier adapter 466 also includes a top face 478, a topchamfer 480, and a bottom chamfer 482. The pressure-barrier adapter 466is supported by the bottom chamfer 482 resting on a shoulder 484 of thetubing head 224. In some embodiments, the pressure-barrier adapter 466is biased against the shoulder 484 by a bottom face 486 of the bypasssleeve 402 contacting the top face 478.

The pressure-barrier adapter 466 may be installed separately, before thebypass sleeve 402, or it may be installed generally at the same timealong with the bypass sleeve 402. To install these components together,a portion of the tool may extend through the bypass sleeve 402 andthread to the pressure-barrier interface 476, as described below withreference to FIG. 29. In some embodiments, the threads on thepressure-barrier interface 476 are opposite the threads 420 on thebypass sleeve 402, and as a result, in these embodiments, threading thebypass sleeve 402 to the adapter 460 with the tool described below alsotends to unthread the tool from the pressure-barrier adapter 466.

In other embodiments, the bypass sleeve 402 may be configured to securethe pressure barrier. In some of these embodiments, the bypass sleeve402 includes the pressure-barrier interface 134 described above withreference to FIG. 2.

FIG. 28 illustrates another example of a bypass sleeve 488 and awellhead assembly 490. In this embodiment, a bushing 492 is threaded to(or is otherwise connected to) an adapter 494. The illustrated bushing492 includes threads 496 that are complementary to threads 498 on theadapter 494. To facilitate relative axial translation of thesecomponents 492 and 494 as they are coupled, the bushing 492 alsoincludes a generally annular groove 500 that is longer than the groove432 described above.

To install the bypass sleeve 488, the bypass sleeve 488 is connected toa tool by the bushing 492 and lowered through the blowout preventer 250.In this embodiment, the bushing 492 carries the weight of the rest ofthe bypass sleeve 488 during an initial portion of installation. Tocarry this weight, the guide members 448 slide to the top of the groove500, at which point the body 404 hangs from the bushing 492. The bypasssleeve 488 is lowered until the body 404 rests on the adapter 466 orsome other portion of the tubing head 224, such as the shoulder 502. Inother embodiments, the body 404 is not supported by the tubing head 224or the adapter 466 until the bushing 492 is partially threaded to theadapter 494. The bushing 492 is rotated by the tool to engage thethreads 498 and 496. As the bushing 492 threads to the adapter 494, thebushing 492 translates axially relative to the body 404, and the guidemembers 448 translate axially through the grooves 500 as they rotatewith the bushing 492. The bushing 492 continues to thread to the adapter494 until the bottom face of the bushing 492 compresses the washer 438against the compression-seal member 440. As with the previousembodiment, the bushing 492 compresses the compression-seal member 440against the shoulder 428, and the compression-seal member 440 expandsradially, sealing against the side walls of the adapter 494.

To remove the bypass sleeve 488, the tool is reattached to the bushing492, and the bushing 492 is rotated in the opposite direction,un-threading the threads 498 and 496. As the bushing 492 un-threads fromthe adapter 494, the guide members 448 both rotate and translate axiallyupward through the groove 500. Before the guide members 448 reach thetop of the groove 500, the threads 496 and 498 disengage, at which pointthe tool lifts the bypass sleeve 488 by the bushing 492. As the bypasssleeve 448 is extracted through the blowout preventer 250, the guidemembers 448 rise to the top of the groove 500, and the body 404 hangsfrom the bushing 492.

In other embodiments, the threads 498 may be disposed on the tubing head224, and the bypass sleeve 488 may be supported by the tubing head 224,without the adapter 494. Or, the bypass sleeve 488 may be supported bysome other component, such as the blowout preventer, a frac tree, or achristmas tree. In some embodiments, the positions of the groove 500 andthe guide member 448 may be reversed, with the groove 500 on an innerdiameter of the bushing 492 and the guide member 448 extending generallyradially outward from the body 404.

FIG. 29 illustrates an example of a tool 504 configured to install thebypass sleeve 488 and the adapter 466 at generally the same time. Theillustrated tool 504 includes a shaft 506, a guide aperture 508, bushinginterfaces 510, a sliding member 512, and an adapter interface 514.

The illustrated shaft 506 is configured to extend through the blowoutpreventer 250 and to support and rotate the bushing interfaces 510, thesliding member 512, and the adapter interface 514. The guide aperture508 is generally complementary to the horizontal cross-section of thesliding member 512 and, in some embodiments, is shaped to allow thesliding member 512 to translate axially relative to the shaft 506, butnot rotate relative to the shaft 506. For example, both the guideaperture 508 and the sliding member 512 may have a generally rectangularshape or some other non-circular shape. The sliding member 512 may becharacterized as having generally one degree of freedom relative to theshaft 506. The illustrated bushing interfaces 510 includeradially-distal members 516 that are configured to selectively engagethe tool interface 444 of the bushing 492. The sliding member 512includes a flange 518, which impedes the sliding member 512 from slidingthrough the guide aperture 508, and an upper portion 520 that is shapedto slide through the guide aperture 508 and transmit torque from theshaft 506.

In this embodiment, the lower portion of the sliding member 512 couplesto the adapter 466 through threads 522. The threads 522 are disposed ona generally circular member 524 coupled to the sliding member 512 suchthat the circular member 524 rotates with the sliding member 512, e.g.,with zero degrees of relative freedom. In some embodiments, the threads522 are opposite (e.g., threaded in an opposite direction relative to)the threads 496 on the bushing 492. As a result, as the bushing 492 isthreaded to the adapter 494, the adapter interface 514 is generallysimultaneously unthreaded from the adapter 466. The rotation of theshaft 506 is transmitted to the sliding member 512 through the guideaperture 508, and as the adapter interface 514 unthreads from theadapter 466, the sliding member 512 slides generally axially upwardthrough the guide aperture 508.

FIG. 30 illustrates another example of a pressure-barrier adapter 524and a wellhead assembly 526. In this embodiment, the pressure-barrieradapter 524 includes a tubing-head interface 528 and a tool interface530, and the wellhead assembly 526 includes an interface 532 that isconfigured to couple to the pressure-barrier adapter 524 through thetubing-head interface 528. The illustrated interfaces 532 and 528 aregenerally complementary threads, but in other embodiments, they mayinclude other structures configured to secure the adapter 524 to thewellhead assembly 526, such as the lock ring 104 and lock-ringreceptacle 252 described above with reference to FIGS. 2 and 4. Theillustrated tool interface 530 includes notches in the upper outerdiameter of the pressure-barrier adapter 524.

The pressure-barrier adapter 524 may be installed in the wellheadassembly 526 before the bypass sleeve 402 (or one of the other bypasssleeves described herein). To install the pressure-barrier adapter 524,a pressure barrier (such as the pressure barrier 255 described abovewith reference to FIG. 5) is coupled to the pressure-barrier interface476, and the pressure-barrier adapter 524 is coupled to a tool with thetool interface 530. The pressure-barrier adapter 524 is then loweredthrough the blowout preventer 250 by the tool and threaded or otherwisecoupled to the tubing head 224. After installing the pressure-barrieradapter 524, the bypass sleeve 402 (or some other bypass sleeve, such asone of the other bypass sleeves described above) is installed, and thefracing process 274 described above with reference to FIG. 12 may beperformed.

FIG. 31 illustrates another embodiment of the present invention. Theillustrated assembly is similar to that which is illustrated in FIG. 15.To manage pressure encountered during fracturing, the illustratedadapter 248 includes an annular recessed portion 331. The recessedportion 331 mitigates the occurrence of bending stresses in the adapter248 and assembly. In the illustrated embodiment, the annular recessedportion 331 is disposed in a bottom surface of the adapter 248. However,in certain embodiments, the annular recessed portion 331 may be disposedin a top surface of the tubing spool 224. In some embodiments, therecessed portion 331 may be machined directly into a lower flange ofequipment, such as a BOP or a frac tree, that can be directly mounted tothe tubing spool 224. Advantageously, the bolts 333 may be formed oflow-strength GR-B7M studs with 80 ksi yield-strength, or GR-Bhigh-strength GR-B7 bolts, or L7 105 ksi yield-strength bolts.

FIG. 32 illustrates another embodiment of the present invention. Theillustrated assembly is again similar to that which is illustrated inFIG. 15. However, in the illustrated embodiment, the bypass sleeve 304is associated with a removable bushing 532. The removable bushing 532may be removable from the bypass sleeve 304 and, as such, may prolongthe useful life of the bypass sleeve 304, as described in greater detailbelow. A radially exterior face 534 of the removable bushing 532 mayinclude one or more seals 536 inside one or more grooves 538. Theremovable bushing 532 is configured to fit securely within the bypasssleeve 304, with the seals 536 forming a seal between the removablebushing 532 and the bypass sleeve 304.

In certain embodiments, a snap ring 540 may be used to lock theremovable bushing 532 in place within the bypass sleeve 304. In otherembodiments, a pin may be used to limit axial movement of the removablebushing 532 relative to the bypass sleeve 304. The pin may be associatedwith a spring which biases the pin radially against the removablebushing 532. The removable bushing 532 may be located at any suitableaxial location within the bypass sleeve 304. For instance, in theillustrated embodiment, the removable bushing 532 is located toward thebottom of the bypass sleeve 304. However, in other embodiments, theremovable bushing 532 may be located toward the top of the bypass sleeve304. In either of these embodiments, however, the removable bushing 532will be removable from within the bypass sleeve 304.

In general, the removable bushing 532 may be configured to hold thepressure barrier 255, such as a backpressure valve, in place within aninterior volume of the removable bushing 532. As such, in theillustrated embodiment, the pressure-barrier interface 134 may belocated on a radially interior face 542 of the removable bushing 532.Due to high pressures generated within the well, strong axially upwardforces may be exerted on the bypass sleeve 304. More specifically,whenever the pressure barrier 255 is used, the threading 544 between thepressure-barrier interface 134 and the pressure barrier 255 may besubjected to these axially upward forces. In addition, the corrosivenature of the chemicals used in the well may adversely affect thelong-term performance of the threading 544 between the pressure-barrierinterface 134 and the pressure barrier 255. However, in the presentembodiment, since both the removable bushing 532 and the pressurebarrier 255 are removable, any component wear will be limited tocomponents (e.g., the removable bushing 532 and the pressure barrier255) which may be replaced more easily than, for instance, the bypasssleeve 304 itself. By limiting wear to these easily removablecomponents, overall costs of production may be reduced. In addition, thelong-term performance of the bypass sleeve 304 may be improved.

Each of the bypass sleeves and pressure-barrier adapters may beconstructed to be a full-bore component. The minimum inner diameters ofeach of the bypass sleeves and pressure-barrier adapters described abovemay be generally equal to or larger than the diameter of the productioncasing 220 (as shown in FIG. 2). For example, in some embodiments, theminimum diameter of certain embodiments may be larger than 5 inches.This is not to suggest, though, that embodiments are limited tofull-bore versions of the devices described above.

Further, each of the embodiments described above may be configured to beextractable through a blowout preventer (BOP) or other equipment coupledto a tubing head, such as a frac tree or a christmas tree. In thesethrough BOP-extractable embodiments, the maximum diameter of the bypasssleeves and pressure-barrier adapters described above may be generallyequal to or less than the diameter of the blowout preventer or otherequipment coupled to the tubing head. For example, in some embodiments,the maximum diameter is less than or generally equal to 8 inches. Again,this is not to suggest that embodiments are limited to throughBOP-extractable versions of the devices described above.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A system, comprising: a wellhead assembly comprising: a tubing headcomprising a first inner cylindrical surface and a top surface a tubularmember comprising a second inner cylindrical surface and a bottomsurface, wherein the tubing head and the tubular member are disposedagainst one another at an interface between the top surface and thebottom surface, and the interface comprises an annular recess; and abypass sleeve disposed substantially entirely within the tubing head andbelow the top surface of tubing head.
 2. The system of claim 1, whereinthe annular recess is disposed in the top surface of the tubing head. 3.The system of claim 1, wherein the annular recess is disposed in thebottom surface of the tubular member.
 4. The system of claim 3, whereinthe tubular member comprises an adapter between the tubing head and ablowout preventer.
 5. The system of claim 1, comprising a plurality oflock screws extending radially through the tubing head, wherein the lockscrews are configured to engage a top portion of the bypass sleeve belowthe top surface of the tubing head.